Before hopping into his helicopter, which was taking off from near the Norfolk and Norwich University Hospital, the actor shook hands with three-year-old Lewis Olsen, and asked him about the pyjamas he was wearing.

Lewis’ dad Nick said: ‘I’d just dropped my wife off for her night shift at the hospital and Lewis had wanted to see the helicopter.

‘He didn’t know who he was meeting. When I got home I went on Google to show him that he’d just met Iron Man.’

The A-list star also met Sarah Gray, who works at the hospital, and she described him as ‘an absolute gent.’

Robert will be reprising his Iron Man role in The Avengers: Age of Ultron (Picture: Getty Images)

She said: ‘He saw us standing, he could have gotten straight into the helicopter. Instead he came over and chatted.’

The Avengers’ A sign could be seen on the Sainsbury Centre’s Modern life Cafe, which also had four high performance cars positioned outside, the Eastern Daily Press goes on.

A giant green screen was also spotted next to the building, as well as groups of actors dressed in blue outfits running backwards and forwards repeatedly in front of the screen.

Some of the film’s stars – including Scarlett Johansson ad Elizabeth Olsen – had reportedly been seen shooting.